Mig welder for aluminium pros & cons

so I need a teflon liner and a bottle of argon/mix, has anyone tried or use a spool gun, they look a bit heavy and could be a long day, do I need to change polarity.

Also it looks like anything under 3mm a TIG is needed.

i did try aluminium welding with mig in 1990 and it did not work. new electronic mig welder like fronius or miller if they do this then its probably now possible. Tig with argon is what is used for stainless and aluminium.
ps i had what you describe in post 1.

Yes, is certainly possible, and can be used for thin metal. My friend used to work at an airconditioning ducting factory and they used an aluminium mig. The welds are not very good looking though.

I used mig for aluminium years ago. You need 100% argon. From memory my welder was a cheapy AC out only. Seemed to work ok. You need to push into the weld not drag like steel welding. Some info on this link.
https://www.prolinesystems.net/files/mig-welding-aluminum.pdf

Straight argon, teflon liner, U grove drive rollers, right sized tips, 5356 wire for 5xxx series aluminium. you will go through a few tips getting it dialed in. I use a cea pulse mig welder, have welded 2mm outside corners easily using the double pulse. Get a stainless steel wire brush and clean, clean and clean again,

Welding Ali is not easy, using a spool gun helps a huge amount because most of the problems occur in the wire feeding,
With normal MIG you need a 4 roller setup, Teflon liner.
Most important is to set the roller tension lightly so that if the roller rubs on the wire, it does not mark it.
If it marks it, it ruins the liner, causes back pressure & lost of contact at the tip, which welds to the wire.
You need to cut the melted ball off the end of the wire before starting a new weld, cut it at a sharp angle so the point will Peirce thru the parent metal oxide & make contact & start the arc, or it will cause back pressure on the wire, bend it, loose electrical contact with the tip, bend wire up thru the liner & cause rollers to slip.
Start you arc at a light, ( low ° angle ) to the workpiece & move towards the weld ( don't drag the gun )
If you grab the wire before the rollers, you should be able to slow the wire down without putting flats on the wire with the rollers, I put the are thru a foam darling before the rollers so to wipe any dust off the wire.

If you have a , say 40° +, angle on the gun/work, you get some backsplatter into the tip, if you feel this during a weld, when you stop, grab the melted ball with your pliers & pull the wire out of the gun, while triggering the wire feed, and roll the wire around the inside of the tip, the wire will grab the splatter or oxide & pull it out with it, then snip the wire at a sharp angle again.

Welding Ali takes a while to get good at it. Even after years I'd still need a day to be comfortable, then a week to get good again, another week to do some just amazing stuff with it. I haven't done much TIG work, it's got its uses but I don't really weld lightgauge metals.
Once you get good at MIG Ali, you can do amazing stuff with any MIG welder.

Post number #6 hits all the points.

Without spool is fine as long as you are using a short feeder tube and a decent gauge wire, I.E. nothing smaller than 0.8 . A stiffer higher magnesium wire like 5356 is definitely the way to go. Preheating is a good idea to reduce possible weld cracking, the expansion coefficient is twice that of steel, but if you use a torch to do so make sure its burning perfectly clean, any deposited crap will screw you.

Electrode positive, just like steel. You are after spray transfer, it should sound like psssssssttt, also be aware that ali is a far superior heat conductor than steel, be prepared for that. The sizzle should only be in the weld ;)